Use variable $_EXTKEY instead of extension key

ext_emconf.php

 <?php
 
-$EM_CONF['slug_extbase'] = [
+$EM_CONF[$_EXTKEY] = [
     'title' => 'Slug updater for Extbase',
     'description' => 'Utility to update slug fields after changing or creating Extbase objects in frontend',
     'version' => '1.0.0',